The Gorden Research Conferences are designed to promote in-depth communication between the most active research workers in rapidly developing disciplines. A number of features of these conferences enhances the extent to which such communication is possible. These include the workshop nature of the conferences, an atmosphere that encourages informal interactions, attendance limitations and emphasis on recent developments. The meetings also provide an excellent forum for participation by new investigators. The 1983 Conference on Hormone Action will be the 13th in a series commenced in 1969 to promote exchange of information about the rapidly expanding field of the molecular mechanism of action of hormones. This includes the field of hormone receptors; hormone entry into target cells; the coupling of hormone-receptor interactions with post-receptor influences; the effects of hormone-receptor complexes on membrane properties; second messengers for hormones, including cyclic AMP, calcium and phospholipids; interactions of hormone receptors with chromatin and the nuclear matrix; effects of hormones on transcription and RNA processing, and other post-transcriptional events; gene structure as related to hormone action; and the reconstitution of hormone-responsive systems with purified receptors, regulatory proteins and gene transfer. The Conference includes discussions of steroid, thyroid, catecholamine and peptide hormones and model systems including cell-free systems with purified genes, receptors and other components; tissue culture systems and animal studies. The clarification of these cellular mechanisms of hormone action has basic application to the understanding of human diseases, including disordered endocrine function, problems of fertility and birth control, neoplastic disease, aging and cardiovascular disease. In addition, this knowledge may suggest and facilitate new and better forms of therapy. Support is requested for travel and subsistence costs of speakers at the Conference.